John: Two is kinda arbitrary, but he’s trying to be provocative, not precise. I think the point is that the number of true priorities you can have is small, maybe much smaller than you might think.

In defense of “two” in particular, IBM did a study once that concluded that that’s the optimal number of projects. It provides some variety, and something to do when one project gets blocked. But as the number of projects increases, people spend more time task-switching and less actually getting work done.

Many years ago I read something about HP employees being given only one objective that would be assessed at their annual appraisal. The idea was that if you had more than one you would have had conflicting priorities. I don’t know if it was true (or still is) but the idea intrigued me, as in my company we’ve always had a long list of objectives.